This invention relates generally to the field of telephony, and in particular to devices for generating static in a telephone line.
In telephone systems, telephone signals are typically carried by metallic telephone cables. A break in a telephone cable where the broken ends of the cable are closely proximate, can cause a fault condition, such as a varying resistance fault, causing static in a phone line. A fault such as a varying resistance fault can cause a disturbance within the frequency band of the telephone signal, causing static or other noise on the telephone line.
A telephone customer who experiences static on his telephone will typically place a service call to the phone company, necessitating the dispatch of a telephone repair technician to the customer""s location. Once at the customer""s location, the telephone technician must find the fault, and repair the break in the line or whatever is causing the static.
Finding a fault such as a varying resistance fault requires the use of an instrument such as a time domain reflectometer (TDR), for example. A TDR is a technologically complex instrument that assists in the characterization and location of faults in metallic cables, including faults such as the varying resistance fault. Training a technician to use a TDR properly is expensive and time-consuming. The problem is magnified because heretofore it has been difficult to reproduce a varying resistance fault in the laboratory. Clearly, it would be advantageous to both telephone service providers and their customers, if technicians were able to learn how to operate equipment such as a TDR in a controlled environment by creating or simulating known faults, rather than to learn xe2x80x9cunder firexe2x80x9d in the field. Thus a need in the art exists for a device that can create static in a telephone line so that technicians can be trained in-house to find and fix faults such as varying resistance faults that create such static.
The present invention satisfies the aforementioned needs in the art by creating a varying resistance fault when the device is installed in a telephone line. The varying resistance fault creates a noisy condition in the telephone, enabling the telephone technicians to be trained to find and fix the faulty condition in a laboratory rather than in the field.
According to the present invention, a device for generating a varying high-resistance fault comprises a housing made of an electrically insulating material, such as a plastic. The housing has an entrance face and defines an interior region of the device. A pair of electrical conductors extends through the entrance face. Each of the conductors has a first portion that extends into the interior region of the device, and a second portion that extends external to the housing. Each of the conductors has a distal portion contained within the housing. The conductors can be copper wires, for example, and can be coated on at least a portion thereof with an insulating sheathing material.
The housing contains a quantity of granular conductive material, such as carbon particles or metal shavings. The distal portion of each conductor is in electrical contact with the granular conductive material, and the quantity of granular material is such that the granular material provides an intermittent electrical connection between the distal portions of the conductors. The distal portions of the conductors can be exposed (i.e., not coated with the insulating sheathing material). Thus, a varying resistance fault causing static can be generated between the distal portions of the conductors by generating a potential difference therebetween.
A method according to the present invention for generating a varying resistance fault includes interposing a static creator such as described above into an electrical circuit by electrically coupling each of the conductors to corresponding conductive members of the circuit. A varying resistance fault can then be generated by applying a potential difference between the distal portions of the conductors to cause an intermittent current to flow therebetween.